PTC heater with flexible printed circuit board

ABSTRACT

An electrically heated chemical delivery system including a heat sensitive chemical and an electrical heater adjacent to the heat sensitive chemical. The heater includes a heater element with a first heater side and a second heater side and a flexible printed circuit in electrical contact with both the first heater side and the second heater side. The flexible printed circuit includes at least one fold allowing electrical contact with both the first heater side and the second heater side.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This is a non-provisional application based upon U.S. provisionalpatent application serial No. 60/357,517, entitled “PTC HEATER WITHFLEXIBLE PRINTED CIRCUIT BOARD”, filed Feb. 15, 2002.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an electrically heated chemicaldelivery system, and, more particularly, to a PTC electrical heaterincluding a flexible printed circuit.

[0004] 2. Description of the Related Art

[0005] A positive temperature coefficient of resistance (PTC) materialexhibits the characteristic that, as the temperature of the materialrises, the electrical resistance of the material also rises. If anelectrical component is composed of PTC material, and if a voltage isapplied to the component, the component will dissipate energy at a rateof V²/R where V is the applied voltage and R is the instantaneousresistance of the component. Unless sufficiently cooled, the PTCelectrical component will heat up as a result of the dissipated energyand thereby increase the material resistance which will decrease theelectrical current through the component and decrease the energydissipation of the component. The PTC component is therefore somewhatself limiting from an electrical current point of view.

[0006] A Positive Temperature Coefficient (PTC) heater circuit appliesan electrical potential on opposite sides of a PTC material to generateheat. As the temperature of the PTC material increases, the electricalresistance also increases. Typical PTC heater circuits use an insulatingfilm and two metal electrodes in proximity to a heatsinking/distributive surface. Although this construction technique iseffective to produce a properly operating PTC heater, it can berelatively expensive in terms of fabrication and assembly.

[0007] What is needed in the art is a PTC heater which is easily andcost effectively fabricated.

SUMMARY OF THE INVENTION

[0008] The present invention provides a PTC heater including a flexibleprinted circuit with printed electrodes on an insulative substrate.

[0009] The invention comprises, in one form thereof, an electricallyheated chemical delivery system, comprising a heat sensitive chemicaland an electrical heater adjacent to the heat sensitive chemical. Theheater includes a heater element with a first heater side and a secondheater side and a flexible printed circuit in electrical contact withboth the first heater side and the second heater side. The flexibleprinted circuit includes at least one fold allowing electrical contactwith both the first heater side and the second heater side.

[0010] An advantage of the present invention is a PTC heater which iseasily and cost effectively fabricated.

[0011] Another advantage of the present invention is PTC material can beprinted on the flexible printed circuit.

[0012] Yet another advantage of the present invention is the flexibleprinted circuit can include additional components, such as a fuse andindicator light with relatively small incremental manufacturing expense.

[0013] A yet further advantage of the present invention is a reductionin the number of parts required to assemble the electrical heater.

[0014] An even yet further advantage of the present invention is anincrease in reliability due to the number of parts reduction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above-mentioned and other features and advantages of thisinvention, and the manner of attaining them, will become more apparentand the invention will be better understood by reference to thefollowing description of an embodiment of the invention taken inconjunction with the accompanying drawings, wherein:

[0016]FIG. 1 is a side view of an embodiment of the electrically heatedchemical delivery system of the present invention showing a flexibleprinted circuit folded around a heater element; and

[0017]FIG. 2 is a plan view of the printed flexible circuit of FIG. 1 inan unfolded state.

[0018] Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplification set out hereinillustrates one preferred embodiment of the invention, in one form, andsuch exemplification is not to be construed as limiting the scope of theinvention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0019] Referring now to the drawings, and more particularly to FIG. 1,there is shown an electrically heated chemical delivery system 10 whichgenerally includes heat sensitive chemical 12 adjacent electrical heater14. Heat sensitive chemical 12 is shown schematically in FIG. 1.

[0020] Heat sensitive chemical 12 can include, but is not limited to,fragrances, insecticides, air fresheners, aromatherapy chemicals,anti-mold compounds, anti-mildew compounds and other 20 chemicals. Heatsensitive chemical 12 can be in the form of capsules, packets, gels,liquids, solids and the like. Heat sensitive chemical 12 and adjacentelectrical heater 14 are typically contained in a suitable housing (notshown). Upon receiving heat energy from heater 14, heat sensitivechemical 12 releases a portion of its chemical to the ambient.

[0021] Electrical heater 14 includes flexible circuit 16 (FIG. 2), whichcan be a flexible printed circuit, folded at least partially aroundheater element 18, and in electrical contact with both first heater side36 and second heater side 38 of heater element 18. Heater element 18 caninclude positive temperature coefficient material 20 which can be anyone of many suitable PTC materials, or combinations thereof.Alternatively, flexible circuit 16 can be in electrical contact at leastone side of heater element 18.

[0022] Flexible circuit 16 includes a flexible insulating substrate 22,electrical traces 24 and indicator light 26. Insulating substrate 22 isformed of any suitable material which is flexible and has preselectedelectrical characteristics necessary for operation of electrical heater14. First circuit side 17 of flexible circuit 16 is shown as includingall of electrical traces 24 and indicator light 26, however, flexiblecircuit 16 can alternatively be a double sided printed circuit or amultilayer printed circuit.

[0023] Electrical traces 18 include leads 28, contact pads 30, 31 andprinted fuse 32. Leads 28 are connected to a suitable source ofelectrical power (not shown). Contact pads 30, 31 electrically contactopposing sides of heater element 18 when flexible circuit 16 is foldedaround heater element 18 (as shown in FIG. 1). Leads 28 are alsoconnected in parallel with each of contact pads 30, 31 and indicatorlight 26. Printed fuse 32 is sized and configured to open at apreselected current therethrough.

[0024] Flexible circuit 16 carries electrical traces 24 thereon and issized and configured to fold around heater element 18, such as at foldlines 34, shown as dashed lines in FIG. 2, and resulting, for example,in folds 40. The number of folds 40 is at least one but can include twoor more as dictated by the application. Likewise, the angle of folds 40,can be 90° as shown or can be other angles depending, in part, on thenumber of folds among other factors such as the flexibility of substrate22 and electrical traces 24. The particular location at which flexiblecircuit 16 is folded may vary from one application to another. Thespecific size, configuration and geometrical shape of flexible circuit16, electrical traces 24 and heater element 18 can be varied dependingon the application.

[0025] The method of assembling electrical heater 14 includes the stepsof electrically connecting a first lead 28 of flexible printed circuit16 to first heater side 36 by electrically contacting first heater side36 with first contact pad 30; folding flexible printed circuit 16 atleast partially around heater element 18; and electrically connectingsecond lead 28 of flexible printed circuit 16 to second heater side 38by electrically contacting second heater side 38 with second contact pad31. Heater sides 36, 38 can be electrically connected to respectivecontact pad 30,31 with solder, conductive adhesives and the like.Electrical heater 14 is assembled with only two separate componentsthereby achieving the aforementioned manufacturing and reliabilityadvantages. Alternatively, positive temperature coefficient material 20can be printed on flexible circuit 16 at either of contact pads 30, 31.

[0026] In use, heat sensitive chemical 12 is located adjacent electricalheater 14, typically by way of a suitable housing (not shown) or thelike. Electrical heater 14 is connected to a suitable source ofelectrical power (not shown) and thereby commences generating heat. Heatfrom electrical heater 14 reaches nearby heat sensitive chemical 12thereby dispersing some of the chemical of heat sensitive chemical 12into the ambient. Indicator light 26 can indicate when power is appliedto electrical heater 14.

[0027] While this invention has been described as having a preferreddesign, the present invention can be further modified within the spiritand scope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

What is claimed is:
 1. An electrically heated chemical delivery system,comprising: a heat sensitive chemical; and an electrical heater adjacentsaid heat sensitive chemical, said heater including: a heater elementhaving a first heater side and a second heater side; and a flexibleprinted circuit in electrical contact with both said first heater sideand said second heater side, said flexible printed circuit including atleast one fold allowing said electrical contact with both said firstheater side and said second heater side.
 2. The electrically heatedchemical delivery system of claim 1, wherein said heater elementincludes a positive temperature coefficient material.
 3. Theelectrically heated chemical delivery system of claim 2, wherein saidflexible printed circuit folds at least partially around said positivetemperature coefficient material.
 4. The electrically heated chemicaldelivery system of claim 1, said flexible printed circuit including aflexible insulating substrate, a first lead electrically connected tosaid first heater side, a second lead electrically connected to saidsecond heater side, both of said first lead and said second lead printedon said flexible insulating substrate.
 5. The electrically heatedchemical delivery system of claim 1, wherein said flexible printedcircuit includes a first circuit side which electrically contacts bothsaid first heater side and said second heater side.
 6. The electricallyheated chemical delivery system of claim 1, said flexible printedcircuit including a flexible insulating substrate, a first lead, asecond lead, a first contact pad, a second contact pad, a printed fuseand an indicator light, said first lead electrically connected to saidprinted fuse, said printed fuse electrically connected to said firstcontact pad, said first contact pad electrically connected to saidindicator light, said second lead electrically connected to both saidsecond contact pad and said indicator light, said first contact padelectrically connected to said first heater side, said second contactpad electrically connected to said second heater side, all of said firstlead, said second lead, said first contact pad, said second contact pad,said printed fuse and said indicator light printed on said flexibleinsulating substrate.
 7. An electrical heater, comprising: a heaterelement having a first heater side and a second heater side; and aflexible printed circuit in electrical contact both said first heaterside and said second heater side, said flexible printed circuitincluding at least one fold allowing said electrical contact with bothsaid first heater side and said second heater side.
 8. The electricalheater of claim 7, wherein said heater element includes a positivetemperature coefficient material.
 9. The electrical heater of claim 8,wherein said flexible printed circuit folds at least partially aroundsaid positive temperature coefficient material.
 10. The electricalheater of claim 7, said flexible printed circuit including a flexibleinsulating substrate, a first lead electrically connected to said firstheater side, a second lead electrically connected to said second heaterside, both of said first lead and said second lead printed on saidflexible insulating substrate.
 11. The electrical heater of claim 7,wherein said flexible printed circuit includes a first circuit sidewhich electrically contacts both said first heater side and said secondheater side.
 12. The electrical heater of claim 7, said flexible printedcircuit including a flexible insulating substrate, a first lead, asecond lead, a first contact pad, a second contact pad, a printed fuseand an indicator light, said first lead electrically connected to saidprinted fuse, said printed fuse electrically connected to said firstcontact pad, said first contact pad electrically connected to saidindicator light, said second lead electrically connected to both saidsecond contact pad and said indicator light, said first contact padelectrically connected to said first heater side, said second contactpad electrically connected to said second heater side, all of said firstlead, said second lead, said first contact pad, said second contact pad,said printed fuse and said indicator light printed on said flexibleinsulating substrate.
 13. A method of assembling an electrical heater,comprising the steps of: electrically connecting a first lead of aflexible printed circuit to a first heater side of a heater element;folding said flexible printed circuit at least partially around saidheater element; and electrically connecting a second lead of a flexibleprinted circuit to a second heater side of said heater element.
 14. Themethod of claim 13, wherein said heater element includes a positivetemperature coefficient material.
 15. The method of claim 13, whereinsaid folding step includes both a first fold and a second fold of saidflexible printed circuit.
 16. The method of claim 13, wherein both saidfirst heater side and said second heater side electrically contacts afirst circuit side.
 17. An electrically heated chemical delivery system,comprising: a heat sensitive chemical; and an electrical heater adjacentsaid heat sensitive chemical, said heater including: a heater elementhaving a first heater side and a second heater side; and a flexibleprinted circuit in electrical contact with at least one of said firstheater side and said second heater side, said flexible printed circuitincluding at least one fold allowing said electrical contact with atleast one of said first heater side and said second heater side.
 18. Theelectrically heated chemical delivery system of claim 17, wherein saidflexible printed circuit is in contact with both said first heater sideand said second heater side.